The present invention relates to a sheet discharge unit for transferring a sheet of pre-treated paper such as a printed paper toward a paper receiving tray and, more particularly, to a sheet discharge unit for use in a printing machine.
Considerable research and development work has been undertaken in the pasts to provide sheet discharge units, one typical example of which is shown in FIG. 15. In FIG. 15, a sheet discharge unit 100 has a transfer passage 102 through which a sheet of printed paper 101 is conducted to a paper receiving tray 107, and a pair of transfer belts 103, 103 are located at a center of the transfer passage 102. The transfer belts 103, 103 move between a sheet transfer starting position and a sheet transfer terminating position. Also, a bottom wall 102a of the transfer passage 102 has a large number of suction bores 104 through which air remaining in the vicinity of the transfer passage 102 is drawn downward such that the sheet 101 is urged toward the transfer belt 103. A pair of left and right jump wings 105, 105 are located in the sheet transfer terminating position at both sides of the transfer belts 103, 103. The pair of jump wings 105, 105 are freely moveable in a pair of guide openings 106, respectively, between a guide position (as shown in FIG. 15) in which the jump wings 105, 105 protrude upward from the bottom surface 102a and a wait position in which the jump wings 105, 105 are retracted downward from the bottom wall 102a. An upper surface 105a of each jump wing 105 is gradually inclined upward along the sheet transfer direction and has a three-dimensional inclined profile wherein each jump wing 105 is gradually inclined from an inside toward an outside. The paper receiving tray 107 is located at a position downstream side of the sheet transfer terminating position and at a position lower than the sheet transfer terminating position. Side fences 108 are mounted at both sides of the paper receiving tray 107, respectively, and an end fence is mounted at a distal end of the paper receiving tray 107.
With such a structure, when the printed sheet 101 is conducted on the sheet transfer starting position of the transfer passage 102, the printed sheet 101 is sucked with air toward the bottom surface 102a of the transfer passage 102 and is urged toward the transfer belts 103, 103. The printed sheet 101 that is urged on the transfer belts 103, 103 is transferred to the sheet transfer terminating position by the transfer belts 103. Here, when the printed sheet 101 to be transferred has a low rigidity, the pair of jump wings 105, 105 are moved to the guide position as shown in FIG. 15. When this occurs, the printed sheet 101 is guided upward at both sides thereof with the pair of jump wings 105, 105 such that the printed sheet 101 is discharged under a state wherein both sides of the printed sheet 101 is curved upward from a central portion. Then, the printed sheet 101 has an increased apparent rigidity and traces a stable dropping trajectory to be dropped to the paper receiving tray 107. In contrast, when the printed sheet 101 to be discharged has a strong rigidity, the pair of jump wings 105, 105 are located in the wait position. In this event, the printed sheet 101 is discharged in a stable dropping state owing to its property of strong rigidity.
Related technologies of the conventional sheet discharge unit 100 discussed above are disclosed in Japanese Patent Application Laid-Open Publication No. H6-239000.
In the conventional sheet discharge unit 100, however, since the pair of left and right jump wings 105, 105 are laterally separate from one another with a sufficiently desired width to cope with printed sheets of various sizes and all of upper surfaces 105a, 105a of the jump wings 105, 105 tend to be brought into contact with surfaces of the printed sheets 101, there exists a relatively large running resistance caused in the printed sheet 101, resulting in a difficulty in discharging the printed sheet to a normal final dropping position. Also, when the printed sheet 101 has the large running resistance, a large amount of paper dust or paper powder is produced owing to wear of the paper. Particularly, the printed sheet 101 is forcedly curved on the left and right jump wings 105, 105 and, therefore, a large running resistance is applied to the printed sheet 101. If, in this instance, the width of the left and right jump wings 105, 105 is decreased with a view to decreasing the running resistance, then, it becomes difficult for the sheet discharge unit to cope with the printed sheet of various sizes.
It is therefore an object of the present invention to provide a sheet discharge unit which can cope with sheets of paper of various sizes and which can reduce running resistance of the sheet of paper and the amount of paper dust or paper powder to be produced from the paper.
A sheet discharge unit of the present invention is provided with: a paper receiving tray; a transfer passage transferring a sheet of pre-treated paper to the paper receiving tray along a sheet transfer direction; guide openings formed at both sides of the transfer passage; a transfer member located in the transfer passage to impart a force to the sheet of pre-treated paper so as to move the sheet of pre-treated paper in the sheet transfer direction; jump wings respectively disposed in the guide openings, and having convex and concave portions arranged in a direction substantially perpendicular to the sheet transfer direction; and actuating member actuating the jump wings between a guide position in which the jump wings respectively protrude upward from the guide openings and a wait position in which the jump wings are retracted into the guide openings.
More specifically, according to one aspect of the invention, there is provided a sheet discharge unit having a transfer passage for transferring a sheet of pre-treated paper along a sheet transfer direction toward a paper receiving tray and having a bottom surface. The sheet discharge unit comprises a pair of left and right jump wings freely moveable between a guide position in which the jump wings protrude upward from the bottom surface of the transfer passage and a wait position in which the jump wings is retracted from the bottom surface of the transfer passage. Each of the left and right jump wings includes a plurality of divided wing components which are laterally spaced from one another in a direction perpendicular to the sheet transfer direction such that, when the jump wings remain in the guide position, the sheet of pre-treated paper is guided upward at both sides thereof to form a curved dropping state and is discharged to the paper receiving tray and, when the jump wings remain in the wait position, the sheet of pre-treated paper is not curved at the both sides thereof and is discharged to the paper receiving tray.
Besides, according to another aspect of the present invention, there is provided a sheet discharge unit having a transfer passage for transferring a sheet of pre-treated paper along a sheet transfer direction toward a paper receiving tray and having a bottom surface. The sheet discharge unit comprises a pair of left and right jump wings freely moveable between a guide position in which the jump wings protrude upward from the bottom surface of the transfer passage and a wait position in which the jump wings remain beneath the bottom surface of the transfer passage. Each of the left and right jump wings includes convex segments for guiding the sheet of pre-treated paper and concave recesses which are out of contact with the sheet of pre-treated paper, the convex segments and the concave recesses being alternately located in a direction perpendicular to the sheet transfer direction such that, when the jump wings remain in the guide position, the sheet of pre-treated paper is guided upward at both sides thereof to form a curved dropping state and is discharged to the paper receiving tray and, when the jump wings remain in the wait position, the sheet of pre-treated paper is not curved at the both sides thereof and is discharged to the paper receiving tray.
Other aspect and advantages of the invention will become more apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.